Why Is My Car Heater Not Working?

There’s nothing worse than getting into a cold car, turning on your heater, and being met with cold air – or nothing at all.

Beyond being stuck shivering in your car, a heater that’s not working can also be a real safety concern, reducing your visibility or hinting at possible engine troubles. Most of the time, getting your heater up and running again is a straightforward fix, but other issues will need a professional to diagnose and solve.

Knowing what to look for is the first step in helping you work out what the problem is. In this guide we’ll walk you through the most common reasons your car heater might have stopped working, the heating parts at fault and when it’s time to get it looked at by a mechanic.

What’s Included In This Article?

• How does a car heater actually work?

• Reasons your car heater may not be working

• Troubleshooting your car heater

  • Your heater isn’t blowing any air at all

  • Your heater is blowing cold air

  • Your car heater only works on high settings

• FAQs

How Does A Car Heater Actually Work?

A car heater works by using your engine and coolant to heat your car.

Your engine generates a lot of heat as it runs, and that excess heat warms up the engine coolant to a very high temperature. The coolant then flows through the small radiator tucked behind your dashboard called the heater core, and a fan pushes that hot air into the car.

So, when you first turn the heating on and it feels cold for a minute or so, that's completely normal; the engine just needs a little time to heat up the coolant first.

Reasons Your Car Heater May Not Be Working

If there’s no heat or air when you turn on your heater, there’s several possible causes for your car heater not working:

• Low coolant level: This is the most common one. Your heater relies on coolant to heat the air, so if the level is too low, you’ll get cold air or nothing at all.

• Faulty thermostat: Your thermostat could be stuck in the closed position, which stops any coolant from reaching the radiator.

• Blown fuse: This could be preventing any power from reaching your heating system.

• Broken heater fan: If the fan is faulty, no air will be able to blow into the car.

• Clogged air filter: Dust can clog the filter and restrict airflow from reaching you.

• Blocked heater core: If the radiator is blocked, the coolant won’t be able to flow through the heater core and heat the air.

If you suspect the issue is anything electrical, or something that requires closer examination, don’t try to inspect it yourself unless you have the required knowledge and skills to do so. We recommend going to a trusted mechanic to keep yourself safe and protect your vehicle.

Troubleshooting Your Car Heater

Still not sure exactly what’s going on? Here’s some of the most common scenarios to help you narrow down what you’re dealing with.

My Heater Isn’t Blowing Any Air At All

If there’s nothing coming out of the vents at all, it’s likely to be an electrical fault or a blocked or damaged part in your heating system.

First, check the air filter (your owner’s manual will tell you where to find this) and if it’s caked in dust, simply swap it out. If the problem still persists, this’ll indicate that it’s a deeper issue that will need to be checked by a professional mechanic.

My Heater Is Blowing Cold Air

It’ll usually take a few minutes for your car’s heater to blow out warm air, but if it’s still cold after a while, your engine coolant might be low, or you could have a problem with your thermostat.

The most likely cause will be your coolant level, which is an easy problem to fix yourself. When the car is off and the engine is cool, check the reservoir and top it up if it’s below the minimum line. If this doesn’t work, it could be a faulty thermostat which is stopping the coolant from creating hot air. It’s best to have this checked by a trusted mechanic, but if you’re doing the work yourself and need a replacement, browse our range of reliable car thermostats.

My Car Heater Only Works On Full Blast

If you can only generate warm air by turning your heating to the highest setting, your rheostat (which adjusts the speed of your heater fan) is most likely at fault. These components naturally wear down as you use your car over time, and so will need to be replaced to solve the problem.

Now that you’ve worked out what might be wrong with your car heater and know your next steps to getting it fixed, you’ll be sat toasty in your car in no time. For more in-depth information on how to keep you and your vehicle safe through the colder months, discover our expert guide on how to protect your car in winter.

FAQs

How Much Does It Cost To Replace A Car Heater?

The cost of replacing a car heater will depend on the problem and what needs to be replaced.

Can I Fix My Car Heater Myself?

If it’s a simple job like topping up low coolant or replacing an air filter, you can most likely fix things yourself. However, for more complex problems like a blown fuse or a blocked heater core, you should always get your car examined by a professional mechanic.

Will My Car Fail Its MOT If The Heater Isn’t Working?

A broken car heater is not an automatic MOT failure as it is not one of the main checks for the safety test. However, if you don’t fix a broken heater, it could lead to further problems which would cause you to fail your MOT.

Is It Safe To Drive With A Broken Heater?

If your heater is broken, it is potentially unsafe to continue driving. The level of danger will depend on the issue with your heater, ranging from reduced visibility from fogged up windows to an overheated engine. Safety should always be your priority, so if you have any concerns, do not risk driving in unsafe conditions.